Science Friday - Dandelion Sensors, GoFundMe Healthcare Shortcomings, Where Did Mars’ Water Go. March 18, 2022, Part 2

Episode Date: March 18, 2022

Flower Power: Floating Sensors Inspired By Dandelions Dandelions’ white puff balls are irresistible—kids delight in blowing on them until the seeds break free, floating away. But, dandelion seeds��� ability to travel through the air is not just aesthetic. Like many other plants, they rely on the wind for seed dispersal. The traveling success of those floating dandelion seeds inspired engineers at the University of Washington to design a new ultra-light sensor. It’s solar powered and weighs just 30 milligrams. The goal is to use these sensors to do things like track temperature fluctuations and survey crops. The researchers’ findings were recently published in the journal Nature. Ira talks with Vikram Iyer, assistant professor of computer science and engineering at the University of Washington, based in Seattle, Washington.   The GoFundMe Healthcare Plan Doesn’t Work Big celebrity crowdfunding campaigns often raise huge sums of money. Take for example, Mila Kunis and Ashton Kutcher, who recently raised $20 million in a week for Ukrainian humanitarian aid. But these types of crowdfunding campaigns are outliers. Increasingly, crowdfunding in the United States is being used as an ad-hoc social safety net. Around a third of campaigns on the most popular crowdfunding site, GoFundMe, are to cover medical costs. And most campaign goals are modest—aiming to raise a few thousand dollars. Yet 30% of campaigns to cover medical costs in 2020 raised zero dollars. Researchers from the University of Washington crunched the data on roughly half a million GoFundMe campaigns for medical expenses to get a better picture of which campaigns are more likely to get funded and which aren’t. Ira speaks with Nora Kenworthy, associate professor of nursing and health studies, global health and anthropology at the University of Washington and Mark Igra, sociology graduate student at the University of Washington.   The Case Of Mars’ Missing Water In the search for life outside Earth, scientists consider having liquid water one of the foremost criteria for determining if a planet could be habitable. On Mars, the evidence for a watery past has been flooding in from rovers and other instruments over the last 30 years. The contents of that water—its temperature and salinity, how fast it moved—are all now written in the planet’s minerals and rocks. SciFri producer Christie Taylor talks to planetary scientist Bethany Ehlmann about the hunt for Mar’s water, where it all went, and whether liquid water could still, somehow, exist on the Red Planet’s surface.   Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Ira Flato. When was the last time you thought about dandelion seeds? You know, maybe as a kid you would blow a dandelion stem until that white puff ball broke apart, and the pieces floated into the sky? Well, those floating dandelion seeds inspired engineers at the University of Washington to design a new ultra-light sensor. It's solar-powered. It weighs just 30 milligrams. The goal is to use these sensors to do things like, well, track temperature fluctuations and survey crops. Joining me now is Vikram Iyer, assistant professor in the Paul G. Allen School of Computer Science and Engineering, University of Washington in Seattle. He's the lead author of a study recently published in the journal Nature all about these tiny pieces of dandelion-inspired tech. Welcome to Science Friday. Hey, Ira, thanks so much

for inviting me. Nice to have you. To start off, what are these floating sensors? used for? What's the problem that they were created to solve? You know, if we if we think about a lot of these scenarios that people are talking about in smart agriculture where we'd like to make measurements of environmental conditions across farms or if we want to evaluate, you know, changing climates and we want to measure temperature, humidity fluctuations across large areas, this is something that's very difficult to do right now because if you want to make measurements across a large geographic area that requires actually going out and placing individual sensors at many different locations. And this can be really time-consuming and expensive.

And you were able to shrink down sensors to be the size of these little tiny seeds that come out of a dandelion? Yeah, exactly. So our motivation here was to address this problem of being able to disperse a large number of sensors automatically over a large area. We looked at dandelion seeds for inspiration. Because if we think about it, these little plants, they can't even move, but they've evolved to spread their seeds over large areas, sometimes distances up to a kilometer. And so by looking at these plants for inspiration, we decided to make these, try to make these sensors as small and light as possible to be able to automatically disperse them in the wind. That's cool. So do they have a battery in them, a tiny little battery? Yeah, one of the things that we had to do here to really cut down on the size and weight is we actually don't have a battery in these devices at all. Instead, what we have is we have these small solar panels.

And so our device after it's deployed, it harvests power from sunlight and it can use that to do its sensing operations and communicate data wirelessly. All right. The geek in me wants to know what they are made out of how they're manufactured, how you disperse them. Yeah, great questions. So the way that we actually make these things is basically by using this laser cutter that can pattern really small features. We start with this really thin sheet of a plastic material, and we put that in our laser cutter, and we can cut all kinds of really fine patterns. And the cool thing about this technique is we can easily change that pattern to vary the amount of time that this is in the air and how far these little sensors are going to disperse. We can actually imitate how, you know, there's some natural variation in individual seeds

where some of them will travel shorter distances, some of them will travel farther to be able to get good coverage over an area. After we cut these little patterns, we can also use the same technique to pattern little wires to make circuits and then attach our electronic components onto them to make our full wireless sensor. And so how do the sensors float through the air? Do you have to shoot them at a certain level? Do they use air currents?

Tell me what's going on there. We design our devices to have what's called a really low terminal velocity. So, you know, think if you drop these from a certain height, they're going to fall to the ground very slowly. And the lower that we can get that number, the more opportunity it has to stay up in the air and the more opportunity it has for the wind to carry it to longer distances. The way that we actually deploy these is we show experiments

where we drop them from a drone. So if we drop them from a drone from, say, 20 meters, about five, six stories in the air, we saw that in a moderate breeze they can fly for up to distances of 100 meters. And how do they keep those little solar panels turned toward the sun all the time? I would imagine you would have to do that. That's actually one of the other features that we leverage in our design by looking at a dandelion seeds for inspiration. If you look at a dandelion seed and you drop it upside down,

you'll notice what happens is it actually flips over in midair and it always lands in the same upright orientation. And so by mimicking this sort of structure, you know, we can make our devices also flip over in midair, even if they're dropped upside down and make sure that they always land in the same upright orientation with the solar cells facing the sun. And so how long do they last? How long do they send back usable information? What's their life expectancy? So these devices could in theory last forever, right? They don't have any kind of battery that limits their lifetime, and they can harvest energy from solar power. So as long as they're outside, they can actually start up even after sunset on the start of a new day when the sun comes out and start transmitting information. Okay, so you've got your launch of these seed-like devices. They fall down. How do they get the data transmitted back to you?

We use this technique called backscatter communication to really reduce both the size and the power of our wireless transmissions. And the idea here is that we're communicating using reflections. So compared to a typical radio like the Bluetooth or Wi-Fi that you have in your phone, those devices are generating a radio signal that goes out into space, which requires both a lot more energy and larger components in circuitry to actually generate that. What we're doing here is if you think of those systems like normal Bluetooth or Wi-Fi as like a flashlight that you're turning on and off to communicate, say, a Morse code style message, what we're doing here instead is we can outsource that flashlight onto another device. And then our really small dandelion sensor, you can think if that is just a mirror that's changing its angle a little bit to either reflect or not reflect that light. And so by doing this decoupling with all of the power expensive components onto another device,

we can make these really, really small devices communicate data wirelessly. And the way that we actually implement that is with a little antenna that's connected to a switch that toggles between two states, one that's very reflective, one that's not. Let's talk about the different uses you could make of this technology. You mentioned about going out, let's say, looking at the temperature or the humidity, of crops in the field. Could you use it to understand crowds of people or traffic or stuff like that? Or what else could you do with it? Yeah, there are certainly lots of applications that you could explore this. As we mentioned, environmental monitoring is one of the first things that comes to mind,

where, you know, we might want to measure things like temperature or your humidity, pressure across a large area. But we could also think of examples like we showed that we can put a little magnetometer on this device that can detect a passing car, for example. We could also think of future applications where we have these little wireless transmitters, right? Can we use that to immediately deploy a large network of connected devices in a place where the wireless infrastructure has been knocked out, for example? The other cool thing about the way that we built this device is it uses a general purpose computing platform that can allow lots of other researchers to build upon this work and adapt it to different applications. To expand a little more on that, compared to having. to design a custom silicon chip from the ground up.

Our devices are programmable. So pretty much anyone with a computer science, computer engineering type degree can easily modify and reprogram the design for new applications. I know in your research, you said that the goal is for a drone to be able to drop, what, a thousand of these centers at once? But what happens to the sensors once they're all out there in nature? I imagine it would be a challenge to go collect a thousand tiny, sensors once they've been scattered. Yeah, that's definitely a great question. And something that we've

been thinking a lot about. One thing to think about in the context of the Eway's problem itself is these devices are pretty small and they actually don't have a battery, right? So compared to all the phones and laptops that get thrown out, they're fairly small by volume, right? But I think when we talk about these examples like environmental monitoring and these remote, hard-to-reach places that I talked about are motivating applications, I think it's really important to try to find ways to make these devices more sustainable going forward. For example, we're thinking about ways to make these devices out of biodegradable materials. For example, rather than like the thin plastic films that we use right now, we could easily make these out of, say, paper, a material that could biodegrade.

And I think in the long term, it'd be really cool to build these devices where we could drop them out for some kind of sensing application and design them so that after a period of time, when we know they're going to be used, they'll just degrade naturally. That's interesting. What's next for this technology? Is this part of a larger project? I know you work in a laboratory that talks about sensors and robots. Yeah, that's a great question.

So really, this is one part of our broader vision on creating what we call the Internet of bio-inspired and biological things. And if we think about it, there's this pretty big gap between biological systems and the capabilities of current, say, Internet of Things and other embedded little sensing devices. Because most of these are pretty big and heavy and they can't move around. And so instead, what we've been thinking about is can we create these tiny battery-free wireless devices that can actually move around, for example, float in the air like these dandelion seeds? Or can we make these little sensors that are small enough to be able to put? put on live insects, for example, like bees, beetles, and we've even used this sort of technology to track the murder hornets that you might have heard about that were found a couple years back

in Washington State. And we can also build on these same technologies by adding, integrating things like actuators to build insect-scale robots as well. I'm fascinated about the insect-sized robotics lab. Can you actually create an artificial insect with a sensor on it? Yeah, so that's actually something that we're working out, kind of as a next step for this work where rather than having to deploy these devices from a drone, could we actually have them fly around themselves to different locations to take these measurements? We could think of lots of scenarios where this could be useful for, say, you know, in disaster-type scenarios, where you, again, don't have infrastructure.

You could think of the example of, say, these little robots flying around to go locate a gas leak or something like that. And the other cool thing that we can do with this technology is once we have these little sensing and computing platforms of this small size. We can also study the behavior of lots of animals like small birds where there really aren't good tools to be able to do this. That's fascinating. Thank you very much for taking time to be with us today. Yeah, it was great talking to you. Vickram Iyer, assistant professor in the Paul G. Allen School of Computer Science and Engineering at the University of Washington, based in Seattle.

We have to take a quick break, and when we come back, we'll be talking about the numbers behind medical crowdfunding campaigns and what it says about our health care system. Stay with us. This is Science Friday. I'm Ira Flato. You're probably pretty familiar with crowdfunding campaigns, right? And some raise huge sums of money in the aftermath of humanitarian crises, like this current GoFundMe campaign by actors Milakunis and Ashton Coutcher. We want to give you a little update on our campaign to stand with Ukraine. We have raised over $20 million in less than a week. But big celebrity-driven campaigns, they're outliers. Increasingly, crowdfunding in the U.S. is being used as an ad hoc social safety net. Around a third of campaigns on the most popular crowdfunding

site, GoFundMe, are to cover medical costs, and most campaign goals are modest, aiming to raise but a few thousand bucks. Yet, 30% of campaigns to cover medical costs in 2020 raised zero dollars. Nata, nothing. Researchers from the University of Washington crunched the data on roughly half a million go-fund me campaigns for medical expenses to get a better picture of whose campaigns get funded and whose don't. Joining me now are my guests, Nora Kenworthy, Associate Professor of Nursing and Health Studies, Global Health and Anthropology at the University of Washington based in Bothal, Washington, and Mark Egra, graduate student in the Department of Sociology at the University of Washington in Seattle.

Welcome to Science Friday. Mark, there's a really big disparity between who is able to reach their crowdfunding goals for medical expenses versus who's not able to do that. Who is more likely to receive funding for their campaign? Well, the people who are most likely to receive funding, are two groups of people, either people who have a large social media following via TikTok or Facebook or something else, or people who are well connected to people who have financial resources to fund the campaign. But for most people who need the funds the most are in neither of those groups. Why is that? We tend to be connected to people like us.

So people with more income tend to be connected to other people with more income. People with more education tend to be connected to other people with more education. And that goes geographically. So we know from data from Facebook that people who live in richer areas like the Upper East side of New York where median household incomes are over $100,000, tend to have friends in other neighborhoods where incomes are high. But, for example, people who live not that far away in Harlem where incomes are low, less than $40,000 median income, friends tend to be in other places where incomes are low like the Bronx.

And so the networks we have dictate the amount of resources that can be given to our campaigns. Nora, do people know this going in? I mean, what are people's perceptions of how well they're going to be able to fundraise when they put up a campaign? I think most people have an expectation of raising maybe a couple thousand dollars. People who are more affluent might have greater expectations of a couple, you know, $10,000. GoFundMe itself tends to encourage people who are setting up campaigns to actually set quite low goals for their campaigns. I think trying to kind of modulate some of the expectations that people bring to the platform. But in our recent paper, we found that, you know, the median campaign for medical expenses in 2020 actually raised only $265. So I think it's safe to say that that is far below what people's expectations are. Wow. Yeah.

Wow. That's shocking. You mean, you could have $50,000, $100,000 you go to a GoFundMe. You expect to get a few thousand and you wind up with a couple of hundreds. Right. And, you know, I think people who raise small amounts of money, sometimes that can still be meaningful support to them, right? But if we think about it in the context of the kind of volume of people's medical bills and health financing needs, it's really a tiny drop in the bucket. And Mark, is that actually more common not to reach your crowdfunding goals? Yes, it is much more common not to reach crowdfunding goals. In this last paper, we showed, that when you find all of the campaigns that people start in medical crowdfunding, we found about a third of them received nothing.

Maybe they were not being distributed. And then only something like 7% received the full amount that they were asking for. Wow. That really is surprising, I think, to anyone who wants to start a GoFundMe campaign, especially about their medical expenses. I mean, let me ask you, Professor Kenworthy, how did the two of you link up to work on crowdfunding research for medical care? Yeah, so both of us come to this project with, you know, our own kind of interest in this

phenomenon. I've been looking at medical crowdfunding since about 2015, I believe. And I came into it with an interest in how people leverage charitable systems to access care and the pitfalls and challenges of relying on charitable systems to provide care. And so my background is public health, and Marks is more the kind of sociological side of things. So I'll let Mark talk about how he comes into this project. Right. Well, my basic interest is altruism and people helping each other.

So I came to this because I also have a background with software and statistics. And so it was a way to find out on a large scale. scale how altruism works and how giving works. Were you shocked that your findings? Let me ask first you, Mark, were you shocked about how few people really want to help other people fund their medical problems? Well, I think I'd put it differently. I wouldn't say that very few people want to help. We actually do find many, many millions of dollars are given and, you know, there are hundreds of thousands of donations given. So I wouldn't say that people, people don't want to give. I think people want to give. The issue is that there's not enough

connection between the people who have the money to give and the people who need the money. Americans are actually lots of research shows that Americans are very generous. One thing that we have written about recently is that GoFundMe is part of a complex sort of social media attention economy in which there is just so much content competing for our attention and for our eyes, and in this case, for our dollars. And so there are really strong algorithmic influences over what gets seen and how content gets pushed to us. And one thing that I think is really clear in the GoFundMe ecosystem is that more successful campaigns tend to be seen more often by people. And so the likelihood of even finding some of these unsuccessful campaigns is really low.

So you're saying, if I hear you correctly, GoFundMe decides what it's going to push out to its viewers to find. And if you're not one of those people, you lose out. Yeah, I mean, like any social media company, there is far more information than any, you know, user could possibly consume from the site. And so they use algorithms. They use search engine features to determine what users see. And they generally push out to users, things that they think will generate the most interest. And in this case, probably the most donations. We talked about GoFundMe pushing campaigns out.

But really, most of the social media sharing is happening on these other platforms. And those platforms all have algorithms that filter what we see. So even though we feel like we are seeing a huge hose of information, we are only seeing a small fraction of what they have available. So there are choices being made for us about what we even see, and those can affect the outcomes. Could someone who needs donations sort of game the system at all? Try to get more people aware of their GoFundMe campaigns, because you see this all the time,

people are saying, I started a GoFundMe campaign, please go to the site and see if you have a few bucks you can give me. Does that help at all? Yeah, it can. One of the things that we have noticed in talking to highly successful crowd funders is that it really helps to have a sort of close team of people who have a lot of expertise in marketing PR. some of these campaigns where, you know, people have pushed really hard to get their message out there. They do see more success. But again, that's also a reflection of the kind of privilege that might be embedded within their social network, you know, that they have friends with this kind of social media expertise and maybe large followings on social platforms. You know, this seems like a predominantly American problem based on our poor health care system. I mean, do we see people in Canada or the UK relying on GoFundMe sites? GoFundMe is certainly popular in other countries as are other kinds of crowdfunding platforms.

And it's important for us to recognize that, you know, the healthcare systems in places like Canada and especially the UK have also faced a lot of kind of retrenchment of social network services through austerity policies. But I think there's a fundamental difference in just the volume and scale of need that we see in the U.S. you know, if I was going to make a generalized statement, I would say in the UK, you tend to see a lot of crowdfunding for maybe experimental procedures that aren't covered under the National Health Service or people who are wanting to get care faster than they're able to under the NHS. In the U.S., it's simply a lot of very basic needs. It's people who are being bankrupted by illness and it's people who do not have adequate health coverage or can't afford their health coverage. and therefore can't afford essential medical care. Now, I understand that about a quarter of Americans have donated to a crowdfunding campaign. How has this changed our perception of how people ask for assistance and who is worthy of receiving a professor? It's such a good question. I mean, I think that our kind of social participation in this new economy has in some ways normalized the idea that we should have a role in picking,

and choosing who has access to medical care. And I think it's important for us to pay attention to what other kinds of health values that might be making less prominent. And most important, I think, is it's sort of occluding this idea that everyone should be deserving of health care, that everyone should have a sort of basic level of health care that they are entitled to regardless of what they look like or how many friends they have or how deserving they are by these kind of complex and often very biased social metrics of deservingness. Mark, when the pandemic first broke out, first few months of the pandemic, did it change what kinds of campaigns people were doing on the site? Well, we saw at the beginning of the pandemic,

a big spike in people requesting both money for things like PPE and support for other people who are affected, but also support for themselves, for their businesses, for basic needs as the disruption was growing. But again, when we studied COVID crowdfunding, we found that many people were not receiving very much money or any money at all. And it turned out that once the government stepped in and started distributing funds to people, that was a much more effective way of dealing with the losses caused by the onset of the pandemic. This is Science Friday from WNYC Studios. Professor Kenworthy, what can be done to change how the crowdfunding system operates

and people's reliance on it to meet their basic needs and their perceived income correct assessment of how easy it is to get that money. I mean, I think part of it is, you know, having conversations like this one, helping people understand what crowdfunding realities look like behind the surface of what we see on the websites. I think it's also important, however, to recognize that I think there are a lot of Americans who see people crowdfunding for basic medical bills and are distressed by that and are not happy that that's our system.

And so we feel it's really important to continue reminding people that there are big structural alternatives to crowdfunding, namely expanding health coverage to more Americans, as well as the kinds of safety net programs that we saw expanded in certain cases during the pandemic. Yeah, fix the system. Fix the health care system. Problem may get a lot less. And I realize that's a big solution, right? So, you know, some of the other stuff that we've been talking about is the importance of, of having more transparency from crowdfunding companies about not just what the outcomes are of crowdfunding campaigns, but, you know, what kinds of algorithms shape what becomes visible and what doesn't? What kinds of corporate decisions are they making about things that might influence the equity and fairness between campaigns? Interesting. You're bringing that up. A few weeks ago, we talked with Dr. David Satcher, who raised the issue and said a lot of people think

that health inequities is about finding the right doctor. It is so much bigger than all of that. And this seems to be just another case of that. So I wrote a paper about differences in returns by race and ethnicity to crowdfunding. And what I found was that it was not that sharing was any different by race or ethnicity or the income of the area where the crowd. funding campaign was started. But it does seem to be the case that because we have this history of things like redlining and job discrimination that lead to lower financial capacity for black and Hispanic Americans, the returns to campaigns started by black and Hispanic Americans are lower. And so we can see this history of, you know,

of racism being reproduced in the kinds of social network-driven charitable efforts that we take. Yeah, I think that's a really important aspect of this research, which is observing the ways that crowdfunding can amplify or reproduce existing social inequities. And that's something that we also put into this most recent paper, the places where people faced more medical debts and were less insured. also the places where they were raising the least amount of money. So we really feel that there are important dynamics that need further exploration here about how these inequities get reproduced. Yeah, something we have talked about in the past and we'll continue to talk about in the future.

I want to thank both of you for taking time to be with us today. Thanks so much for having us. Thanks. Nora Kenworthy, Associate Professor of Nursing and Health Studies, Global Health and Anthropology at the University of Washington, based in Bothell, Washington, and Mark Igra, graduate student in the Department of Sociology, at the University of Washington in Seattle. We have to take a quick break, and when we come back, in the last 30 years, the evidence has piled on.

Mars once had water. We only have three planets in our solar system where we not only get a snapshot of habitats, but we have the potential to understand the billion-year history of what processes sustain those habitats, and water is really key to the solar system. equation. But where is that water now? And could life have thrived there? Stay tuned. This is Science Friday. I'm Ira Plato. It's the aides of March this week, or maybe I should say

the Iids of Mars. Yes, as the Sci-Fry Book Club has been digging deeply into the red planet's potential for hosting life with the book Sirens of Mars by Sarah Stewart Johnson. We've already talked about meteorites, rock samples, and the limits of life as we know it. And we've got another close up on the planet Mars for you with producer Christy Taylor. Hey, Christy, what are we in for today? Hey there, Ira. Today we are going to talk about water on Mars. I remember that a couple of hundred years ago, astronomers thought they saw lines on Mars that might be canals, right? Yeah, they did. And Ray Bradbury, he even wrote about whole cities centered on those. canals in the Martian Chronicles, kind of like Venice. Those lines, unfortunately later proved to be

optical illusions, and our closer looks at Mars were first kind of disappointing. When Mariner 4 sent images back, Mars looked like a dead, dry desert planet. But then it got really exciting as we got closer and closer looks. They revealed a world that was probably shaped by past water. We've got river deltas, lake beds, valleys carved by moving water, maybe even oceans. Yeah, and what I really like about the story as that there are some people today who think liquid water could potentially still be there. Yeah, that's so interesting. And I talked to Dr. Bethany Elman. She's a professor of planetary science at the California Institute of Technology. She's also president of the Planetary Society. And she's one person who is currently investigating the history of water on Mars and the potential

for liquid water to still be there on Mars. And we started by talking about why the question of water is so interesting and important in the hunt for life. One of the reasons that I am so excited about exploring Mars and Venus is that we only have three planets in our solar system where we not only get a snapshot of habitats, but we have the potential to understand the billion-year history of what processes sustain those habitats, and water is really key to this equation. And over the last 30 years or so, we've been learning with increasing certainty that Mars itself once had liquid water.

What were some of the biggest pieces of evidence along the way to that understanding? The decades of Mars exploration that we've been doing keep getting more and more hints of this once watery world that was once far more Earthlike. The first hints came with the first missions, the first fly-by missions of mariner space probes and the Viking orbiter's and landers. Because in those images, we saw the evidence of past valleys and canyons, some of which were carved by liquid water. Since then, though, the story has really taken off in the 2000s when we started to see the chemical and mineral fingerprints of water. So not just water maybe for a relatively short period of time in a violent flood, but over millions of years, transforming the chemistry and mineralogy to leave fingerprints of what the environmental conditions were. What are those, when you say fingerprints, what are we talking about? Some of the fingerprints of water that we've seen are from orbit in using infrared spectra.

So intensity of light coming back in reflectance or emitted light as a function of wave. length. You see these characteristic absorptions or peaks. And each of those indicates a particular mineral phase. We've also had the enormous opportunity to send rovers to a few of the interesting spots that we've spied from orbit where some of the fingerprints of water can be seen with the chemistry and mineralogy instruments on the rover mass spectrometers and all of the chemical tools that we can throw at the planet. How does a mineral tell a story of water? What is in the mineral that really gives that evidence? You know, we toss around these terms rock and mineral, but a mineral is something very specific to a geologist. It's an inorganic element or compound that has a fixed structure

and a characteristic chemistry. And why that's important is that minerals form and response to the conditions around them. So in terms of minerals related to water, they're really key indicators for what the environments were like. What was the temperature of the water? What was the pH of the water? Was it salty? Was it fresh? Was it incredibly hot? So these are some of the things that we can tell from minerals, whether because you get different minerals in different settings. You get you get salts, you get clay minerals, iron oxides from rust. All of these are indicators of the environment. What are some of the minerals that indicate like hot water or salty water or acidic water? Yeah, well, let's get like nerdy with minerals here for a moment. One of the most exciting minerals. that we found from orbit when we were first looking at data from Chrism, the compact reconnaissance imaging spectrometer from Mars.

We're looking at the reflected light, and we see the fingerprints of this particular mineral called prenite. It's this beautiful greenish mineral. It's a calcium aluminum silicate mineral that has water in its structure. And prenite was one of these things we didn't expect to find. It doesn't occur in huge amounts, but it was there in small amounts. We could see it like in certain rock formations and not others.

And what's important about it is it actually forms under pretty restrictive conditions that are only hot about 200 to 400 degrees Celsius. So when we saw this mineral on Mars and we saw it associated with some really ancient terrains that were kind of like cut into canyons and we could look at the wall. And then we also saw it in impact craters in ejecta thrown out and in the central peaks. We knew that those areas had once had warm waters flowing through them because this beautiful greenish mineral preenite that you could see in the Natural History Museum was sending off its, you know, had a spectral signature that was appearing in some of the rocks that we were seeing from orbit. That's so cool. Well, then what is the story of this water's existence on Mars? You know, we have on Earth this set of environments that include things like salt marshes and subglacial lakes and deserts. Like, how do you describe what we know about the story of Mars' past environments?

I would say that minus the plants. We had all of those environments on Mars, too. And that has been the big discovery, really, of the last, I'd say, 20 years of exploration, driven by both the orbiters and then the rovers that have been able to follow up at some of these sites. Mars had a diverse set of aqueous environments that varied in space, varied as a function of time, much like our own planet. So, you know, just to rattle it off, we had hydrothermal systems, we had aquifers deep underground, we had rivers on Mars, lakes, shallow ponds of salty waters. Sometimes those ponds were acidic. We know that there are a few impact craters that had volcanic hydrothermal systems coming out of the bottom, like lost city hydrothermal systems.

And we had environments where soils were forming. We can see the soil horizons, you know, kind of sliced in the canyons of Mars. So for about two, two and a half billion years, Mars hosted an environmental diversity that was comparable to Earth. The headline, Water on Mars has perhaps been overused over the last. last 20 years, but it because it has the evidence over and over and over again, and we get this picture of a rich, habitable world full of potential environments that could have hosted life. That's incredible. And at some point, Mars lost this liquid water. We know some of it is in ice, but what do we think happened to it? That's right. So Mars, unlike Earth, was not able to sustain

a richness of habitable environments over four and a half billion years, the way Earth has for its life here. Now, there may still be Martian environments underground. The jury's still out, whether there are underground aquifers of liquid water on Mars. And we do think there might be small amounts of liquid water that come and go on the surface even today. But Mars lost its water. And we've been scratching our heads, why? But I think we're starting to piece together that picture, that some of the water is now trapped in ice, as you said. Some of the water has been lost to space over time. And some of the water has actually been lost to the crust itself, trapped in these minerals, some of which themselves have water. A paper earlier this year by myself and grad student

Eva Scheller calculated that maybe 30 to 90 percent of Mars water was sucked into the crust. And unlike Earth, Mars doesn't have plate tectonics to recycle that crust down into the mantle and then the water back up through volcanoes. So it's a one-way street once that water gets trapped in minerals in the crest. Wait a minute. So volcanoes are a water recycling mechanism on Earth? So believe it or not, yeah, one of the ways that a lot of Earth's atmosphere built up and acquired its water is from volcanoes. We think of them as destructive forces.

But, you know, one of the other things that happens is when a volcano erupts, it releases gases in the atmosphere. These gases include H2O. Earth's mantle has water in it. And so when we tap that through volcanism, water can get released. This replenishes the water in our atmosphere. That's naturally lost to space, lost by, stripped away by the solar wind, lost by thermal escape. But also importantly, on plate tectonics, our mantles, water is getting refreshed. And some volcanoes have more water than others because of the subduction of ocean crest, hydrated ocean crest that has minerals in it that formed from water, you know, get subducted down and the mantle carry that water in there. And then some of that comes out via volcanoes. So it's like a giant volcanoes and

plate tectonics are a giant recycling mechanism for water. Another recent piece of research that you put out actually suggests the water on Mars stuck around a lot longer than we thought, maybe as much as a billion years. How can you tell something like that? Yeah. So one of the things that we're trying to do as now that we have seen all these interesting water-related environments on Mars, as we're trying to figure out, okay, when in Mars history did Mars host water? So one of the most enigmatic deposits were the set of chloride pond. So chloride is N-A-C-L, table salt, and scattered throughout the southern highlands of Mars. This is some of Mars's most ancient terrains, kind of undulating hills and valleys and deep craters and some volcanic flows, scattered across.

there in these kind of little irregular depressions were chloride salts. And they, at one point in Mars history, they would have been, you know, shallow ponds of salty water sitting on the, on the surface of Mars with grad student, former grad student now postdoctoral scholar, Dr. Ellen Leesk, we took a look at how old were some of those chains of lakes, chains of salty ponds that we were seeing. And we did that by doing a technique called crater counting, where you, you count the number of craters in whatever terrain is under those lakes because those lakes have to be younger than whatever they're sitting upon. And so you basically count the number of craters under those lake deposits. And you compare that to the density of craters elsewhere on the surface.

And we, using those crater chronologies, we determined that, you know, these salty lakes meant flowing water on the surface of Mars as recently as two billion years ago. And that is still, long time ago, but it's about a billion years later than the terrains that we're currently exploring with the curiosity and perseverance rover. So those lakes are about three billion years old. These salty ponds were about two billion years old. So then the question becomes, well, are there even younger deposits or younger examples of liquid water on the surface of Mars? I'm Christy Taylor, and this is Science Friday from WNYC Studios. We're talking about water on Mars with Dr. Bethany Elman. I mean, is it possible that there could still somehow be water on the surface of Mars even today, or is that completely out of the question?

The pendulum has gone back and forth as to whether there could be liquid water on the surface today. I think for a long time people thought that the answer was no. I mean, it is cold. The atmosphere is incredibly dry. Certainly thermodynamics at this moment, the water is unstable to both sublimation as well as evaporation. as well as evaporation, if you did get liquid water on the surface. However, when we've explored with the rovers, we have found these tantalizing hints of an active Mars. For example, you've covered this before, methane on Mars. It comes, it goes, there's something happening that's driving that. Is

it water? We don't know. We've also seen hydras salts that pass through a phase called deliquescence where they can let off their water. Now, this is small amounts of water, but water and mineral structures in the course of a day, in the course of the season, the salt can effectively breathe in and out the water as liquid water. It's called deladolescence. But the evidence that I always think about that I just think is tantalizing is, you know, the Spirit Rover, when it was driving and it got its bum wheel late in history and it had to kind of drag this wheel around. It was sort of fortunate. It was like this trenching experiment on the go. And one of the days when we turned around after the drive, it had dragged through this like large salt deposit, you know, a few feet wide. The upper, upper few

inches or centimeters of for being scientific, portions of the surface that had been churned by that wheel had turned up these yellow and white salts just, you know, just like just beneath the surface. And, you know, those wouldn't have sat there stable for four billion years with all the wind coming and going in the sands. So they must have been formed by water passing through the soils, you know, at least within a few million years, if not sooner. And so I think Mars has a climate perturbor that Earth doesn't have to the same degree. Mars is tilts on its axis. It tilts its obliquity leading to climate change on the scale of hundreds of thousands to millions of years. And I think This sometimes tilts Mars into a regime where water and trapped gases are released from the polar caps making liquid water more stable on the surface.

And I think that we may be seeing hints of that. Well, with that in mind, is there anywhere in particular on Mars that you want to personally walk around on with your suite of geologic instruments? It would be incredible to be the first astronaut on Mars. In the meantime, I will settle for sending some robotic mobile explorers like rovers or helicopters. You know, I always struggle to answer this question because the reality is that if we want to piece together the question of Mars' climate, explore its past habitats and really look for life, we now have dozens, if not hundreds of places that are ideal to explore on the surface. So I really think we're transitioning to this point in Mars exploration where it's important to get, you know, boots on the ground, so to speak, whether they're astronaut boots or rover wheels or helicopter landing foot pads. Getting to some of these sites where we have this rock record of liquid water is, I think, incredibly important so that we can look for evidence of water, understand the watery environment and the conditions that sustained it as well as look for life in multiple times of ancient environments. And then there are places, you know, with recent salts, with ice just at the surface that I think are good to look for modern water and potentially modern life.

So I'd love to go also to some of the ice deposits and some of these recent salt deposits. So many places to explore. And so little time. Well, thank you so much, Bethany for the time today. My pleasure. Dr. Bethany Elman is a professor of planetary science at the California Institute of Technology and president of the the planetary society. She's based in Pasadena. Great story, Christy. Thank you. So much Mars to explore. I get it. Well, that's got me excited and impatient for the next mission to Mars, whenever that might be.

Thanks so much, Christy. Thank you, Ira. And if you've been dying to talk to Sirens of Mars author, Sarah Stewart Johnson, another planetary scientist, you're in luck. She's answering questions in a live Zoom taping next week. and you can learn more about the mysteries of Martian geology, visit ScienceFriiday.com slash Mars event to sign up. ScienceFriiday.com slash Mars event. And that's about all the time we have for this hour. If you missed any part of the program or you would like to hear it again,

subscribe to our podcasts or ask your smart speaker to play Science Friday. Have a great weekend and happy spring equinox. We'll see you next week. I'm Ira Flato.